Creating a permanent or near permanent tattoo on a person requires placing indelible ink into the dermis layer of the skin. The indelible ink is generally permanent and is not absorbed by the body or transported out of the body when placed in the dermis layer of the skin. The ink is placed into the dermis through a needle, which is generally part of a tattooing machine, often called a tattoo gun. The needle often contacts nerve endings, which can cause pain for the tattoo recipient.
Generally, tattoo machines operate by oscillating at least one needle at a rapid speed (e.g., 80 to 150 times per second) into and out of a person's skin. The needle's penetration may be adjustable, but generally, the needle penetrates between 1 mm and 4 mm beneath the surface of the skin. The needle carries ink and deposits the ink into the person's skin. Tattoo machines typically come in two primary variations: coil machines and rotary machines. Coil tattoo machines utilize electromagnetic coils with springs that oscillate an arm up and down, which drives the needle oscillation. A rotary tattoo machine uses a motor and a cam, which drives the needle oscillation. In both machines, the needle penetration depth remains generally the same during a single use. Manual adjustments between tattooing operations work to vary the needle penetration depth.